1. Field of the Invention
The present invention relates to reed valves for controlling air intake into internal combustion engines, and, more particularly, to an improved design for single and multiple stage reed valves for such engines.
2. Description of the Prior Art
Reed valves are presently widely employed in internal combustion engines to control air or air/fuel intake. In two-stroke cycle engines, such as disclosed in U.S. Pat. Nos. 3,905,340, 3,905,341, and 4,051,820, such reed valves play an important role in supporting the improved operation of the engine and the proper transfer of air and fuel from crankcase to combustion chamber. More recently, such reed valves also have been employed in four-stroke cycle engines to control air intake and improve engine performance.
In U.S. Pat. No. 3,905,340 it is shown that significant improvements in reed valve life and performance may be achieved by substituting a "vented" or multiple stage reed valve design in place of a conventional single stage reed. In the design disclosed in that patent, a relatively stiff primary reed is utilize having ports therein; this valve member is designed to be just flexible enough to open fully only under the greatly decreased internal engine pressure encountered at higher engine speeds (although it has been found that optimum performance is achieved if some opening of the primary reed valve occurs each engine cycle). A secondary reed member is then oriented over the ports in the primary reed, with a secondary reed petal sealing each of the primary reed ports. The secondary reed member provides fluid flow each engine cycle through the ports in the primary reed member. In order to allow such flow, the secondary reed members are far more flexible than the primary reed so that the secondary reed member opens farther than the primary reed during the pressure changes each engine cycle. The invention of the '340 patent improves engine performance in virtually all applications and, due to the reduced stresses inherent with this design, reed valve life is dramatically increased.
Although the multi-stage reed disclosed in U.S. Pat. No. 3,905,340 functions very well, it has been found that further improvements may be possible to that design. One problem that has been encountered is that many intake passages have uneven flow distribution through them which results in greater stress placed on certain petals of the secondary reed. As a result of the increased stresses placed on only some of the reed petals, the over-stressed petals will undergo material fatigue and break far more rapidly than less stressed reed petals. Further, with uneven flow distribution through the air intake, conventional or multi-staged reeds do not provide optimum air intake into the engine. One solution to this problem is addressed in U.S. Pat. No. 4,879,976 for an aeroform reed valve cage which modifies the intake passage upstream from the reed valves so to provide more even air flow through the reed valves. Even with this advance, additional improvements in reed valve performance and petal life are believed to be possible.
Accordingly, it is a primary object of the present invention to provide an improved reed valve which provides all the benefits of prior multi-stage reed valves while having improved flow characteristics, improved performance, and increased operating life.
It is a further object of the present invention to provide a reed valve with the above advantages which is straightforward in design and adds minimal weight, complexity, or expense to the engine or the air intake system.